A maleimide compound is solid or liquid at room temperature so it is stored in various forms. For example, a solid maleimide is handled in the form of tablets, flakes, powders, etc. at room temperature and the forms thereof during storage such as flake container bags, drum containers, gallon containers, paper bags, tank containers are varied. Maleimide compound in heated molten state is stored in storage tanks in a liquid state.
There has been a problem that the color of the maleimide compound is changed gradually to a blown color, and sometimes into a slightly bluish black brown color, when it is stored in such a solid or liquid state. The rate of discoloration of the maleimide compound varies depending on state, form and storage conditions of the stored maleimide compound, and the discoloration of the maleimide compound during its storage is inevitable although it can occur quickly or slowly.
Discoloration of the maleimide compound is an important problem when used. That is, since the maleimide compound itself is a kind of raw monomer used for improving heat resistance of various thermoplastic resins such as styrene type resins, e.g., AS resin and ABS resin, methyl methacrylate resins, and vinyl chloride resins, etc., the discoloration of the maleimide compound makes the various thermoplastic resins discolored, and as a natural result, the commercial value of the thermoplastic resins decreases considerably. Thus it is necessary to solve the discoloration problem just mentioned above.
Accordingly, an object of the present invention is to provide a stabilized maleimide compound which is hard to discolor during its storage.